Category: The Conversation

Source: The Conversation – Global Perspectives – By Craig Dalton, Conjoint Associate Professor, School of Medicine and Public Health, University of Newcastle

The cruise ship cluster of hantavirus cases continues to grow. The World Health Organization reports that as of May 6 there were eight cases, three of whom are confirmed by laboratory testing as hantavirus. In recent days, we heard three passengers had died.

Now some passengers are being medically evacuated from the cruise ship MV Hondius. Other passengers have disembarked and are returning home. Swiss authorities have confirmed a passenger on the ship is now a confirmed case and is receiving care in a Zurich hospital.

I’m a public health physician with a special interest in respiratory diseases. I’ve also investigated a hantavirus outbreak.

Here’s what investigators want to know about the current cluster of cases. This includes gathering evidence to see if the virus is transmitting from person to person.

Back in 1993, there was an unknown pathogen

In 1993, I was a young epidemic intelligence service officer working at the United States Centers for Disease Control. I was deployed to the deserts of the south-western US to help investigate a frightening outbreak, mainly among Navajo people.

Adults in their 20s and 30s were becoming suddenly unwell. They would develop a fever and cough, then rapidly progress to severe respiratory failure as fluid leaked into their lungs. Some appeared well enough to be dancing in the evening and were dead within hours.

The investigation team was nervous. We did not yet know the pathogen, how it was spreading, or whether we were at risk.

One of the first recognised cases was a well-known runner, so we initially wondered whether infection might be linked to inhaling something stirred up in desert dust. A leak from a remote military biowarfare laboratory was also considered, as was plague that was endemic to the area.

After laboratory testing, the cause was identified as a new hantavirus, later known as Sin Nombre virus. The virus attacked the small blood vessels of the lungs and was linked to exposure to the urine, faeces and saliva of infected deer mice. Mice numbers had increased dramatically and were entering homes and workplaces across affected communities.

A crucial finding was that, like most hantaviruses, Sin Nombre virus did not appear to spread from person to person. Family clusters were explained by shared exposure to rodents or rodent-contaminated environments, especially during cleaning or other close contact with contaminated objects or dust.

That is why many of us were surprised years later when Andes virus, a South American hantavirus, was shown to spread occasionally from person to person.

This remains uncommon, but it has been documented, including in outbreaks in Argentina – the country from which the MV Hondius departed before the current suspected outbreak.

What would a disease detective do now?

The first step in any outbreak investigation is to confirm the diagnosis. At this stage, the difference between a “suspected” and “confirmed” case still matters.

Investigators need to know whether all severe respiratory illnesses in the cluster are due to hantavirus, or whether confirmed cases are occurring against a background of another infection, such as influenza or COVID.

The next step is to build a timeline. The timing of when symptoms started is often the first clue to where and how people were exposed.

According to WHO, the ship departed Ushuaia, Argentina, on April 1 2026. The first known case developed symptoms on April 6. Other cases developed symptoms later in April.

Let’s focus our attention on the first three cases.

Hantavirus pulmonary syndrome describes the respiratory symptoms that follow after the type of hantavirus infection that mainly attacks the lungs. These typically develop two to four weeks after exposure. However, illness can appear as early as one week and as late as eight weeks after infection.

That makes the first case difficult to explain as an exposure acquired on the ship after departure. Symptoms started on April 6, only five days after leaving Argentina. That’s shorter than the usual incubation period (the period from infection to showing symptoms) and even shorter than the lower end commonly cited.

So for that case, it’s more plausible for that person to have been exposed in Argentina before boarding. There are emerging reports of a bird-watching activity that might have led to rodent exposure.

The later cases are more ambiguous. They could have been exposed before departure, or during shore activities in Argentina, or elsewhere. But their timing also raises another possibility: transmission from the first case to close contacts on board.

This is where the epidemiology becomes interesting.

Did the virus spread from person to person?

The second case was a close contact of the first. This creates two plausible explanations. They may have both been exposed to the same infected rodent (or its urine or droppings, for example). Alternatively, it’s very likely the second case contracted the infection from the first case.

The third case was not part of that same close family unit. If investigators find this person shared the same excursions in Argentina as the first two, the outbreak may still be explained by a common source. But if there was no shared rodent exposure, suspicion of person-to-person transmission increases.

This does not mean person-to-person transmission is proven. It means it becomes one of the leading hypotheses to test.

If human-to-human transmission is not the explanation, investigators would need to consider a less tidy chain of events.

The first case would have had a pre-boarding exposure with a short incubation period. The second case would need either the same exposure with a longer incubation period, or infection from the first case.

The third case would need either an independent exposure to infected rodents before boarding, or another exposure during the voyage. None of these is impossible. But as more cases appear, and if they cluster in time around contact with earlier cases, the human-to-human hypothesis becomes harder to dismiss.

The approximate gap between the first case’s illness and the later cases is also important. If person-to-person transmission is occurring, severe hantavirus illness is likely to coincide with a higher risk of being infectious and infecting others. So we would expect symptoms that start two to three weeks after close contact with an earlier severe case, and this is what we’re seeing from the cruise ship.

What are the public health implications?

The practical public health response must therefore cover both possibilities: a common environmental source and limited person-to-person spread.

That means detailed interviews about pre-boarding travel, shore excursions, wildlife exposure, rodent sightings, cabin locations, cleaning activities, shared dining, shared transport, and close contact with ill passengers.

It also means laboratory confirmation in multiple cases, sequencing of viral samples where possible, and careful reconstruction of who had contact with whom, and when.

Genetic fingerprinting can explore if the virus has the same historical mutation that allowed human-to-human transmission to emerge in previous outbreaks (which were easily controlled with basic isolation and infection control). If a new mutation was found, this would raise concerns of greater transmission risks.

For the public and health authorities considering receiving the passengers from the quarantined ship, the key message is not to panic.

Most hantaviruses are not spread between people. Even with Andes virus, person-to-person transmission is uncommon and usually requires close or prolonged contact. WHO currently assesses the risk to the global population as low. This virus does not spread like influenza or COVID.

But for outbreak investigators, this is exactly the sort of cluster that demands disciplined shoe-leather epidemiology: confirm the diagnosis, build the timeline, test the competing hypotheses, and let the pattern of exposure, illness and laboratory evidence tell the story.

Craig Dalton receives funding from the Commonwealth Department of Health, Disability and Ageing.

– ref. I’ve investigated a hantavirus outbreak. Here’s what I can tell you about the cruise ship cluster – https://theconversation.com/ive-investigated-a-hantavirus-outbreak-heres-what-i-can-tell-you-about-the-cruise-ship-cluster-282365

Source: The Conversation – Global Perspectives – By Erik D Reichle, Professor of cognitive psychology, Macquarie University

The Swedish government recently announced it was moving from the classroom use of digital devices back to physical books. It cited concerns over declining test scores and increasing screen time.

Are these concerns well founded? And what does the science of reading say about the possible consequences of reading on digital devices versus books?

To address these questions, it’s worth remembering that, although reading might appear to be an easy task, this impression is false. Reading is arguably the most difficult task one must learn – one that requires years of formal education and practice to master. In contrast to spoken language, it is a skill we are not biologically predisposed to learn.

Millions of Australians, both children and adults, struggle with literacy.

In this series, we explore the challenges of reading in an age of smartphones and social media – and ask experts how we can become better readers.

Why is reading so difficult?

To understand why reading is difficult, one must first understand the physiology of reading.

As you are reading this sentence, your eyes are making a series of rapid movements, called saccades, from one word to the next. During these saccades, the processing of visual information is suppressed and is only available during brief intervals, called fixations, when the eyes are stationary.

Experiments that measure readers’ eye movements have shown we fixate most words because our capacity to extract visual information during each fixation is extremely limited.

In languages like English that are read from left to right, our capacity to perceive the features that distinguish letters is limited to a small region of the visual field called the perceptual span. This span extends from 2-3 letter spaces to the left of fixation to 8-12 letter spaces to the right of fixation.

The span’s asymmetry reflects the movement of attention through the text. It extends to the left in languages like Arabic, which are read from right to left. The size of the span is smaller for dense writing systems, such as Chinese.

We also know from eye-tracking and brain-imaging experiments that words require time to identify. Our best estimates suggest visual information requires 60 milliseconds to propagate from the eyes to the brain and words then require an additional 100-300 milliseconds to identify. (A millsecond is one-thousandth of a second).

These constraints limit the maximum rate of reading to 300-400 words per minute, depending on the difficulty of the text and one’s level of comprehension.

Speed-reading advocates, who falsely promise faster reading speeds, teach you how to skim a text. Comprehension declines at a rate inversely proportional to the gain in speed.

Importantly, the upper limit for reading speed requires years of practice to attain, because it requires the brain systems that support vision, attention, word identification, language processing and eye movements to operate in a highly coordinated manner. Anything that prevents this coordination will therefore reduce comprehension.

Consequences of digital reading

So what are the likely consequences of digital reading?

With some devices, such as e-readers, there is little reason to suspect digital reading differs from the reading of books, because both formats support the mental processes required for skilled reading.

The more questionable devices are those introducing distractions (such as news websites interspersed with ads) or which have suboptimal formatting, such as centre-justified text with large or unequal-sized gaps between words. The latter is rarely a feature of paper-based texts.

Although the consequences of these two factors are under-researched, enough has been learned about human cognition to make informed predictions.

For example, images and audio unrelated to a text such as pop-up ads can capture attention. Although most adults have developed a level of executive control sufficient to ignore such distractions, young children have not.

The implications for a child who is struggling to understand the meaning of a text are obvious. Their comprehension will suffer to the extent that additional effort is required to ignore distractions, or if they do not yet have the mental coordination to understand the text has been disrupted.

There is also evidence from eye-tracking experiments that many digital environments, such as webpages, can induce specific reading strategies, such as skimming for gist or searching for information.

Although such strategies might be adaptive in some contexts, they reduce overall comprehension. This possibility should be especially concerning for children, because years of practice are needed to coordinate the mental systems that support adult levels of reading skill.

Such concerns have recently drawn more attention, because the onset of the COVID-19 pandemic caused a shift to online education and a marked increase in digital reading. Although these changes were motivated by practical necessity, their long-term consequences remain unclear.

So far, eye-tracking research has been carried out on computer screens. New technology is becoming available which will allow us to directly compare eye movements and comprehension between digital devices and paper. This should give us more clarity about the benefits versus costs of digital devices.

Given reading ability is predictive of one’s education, socioeconomic status and wellbeing, the importance of assessing the long-term consequences of digital reading cannot be overstated.

Erik D Reichle has received funding from the US National Institute of Health, US Institute of Education Sciences, UK Economic and Social Research Council, and Australian Research Council.

Lili Yu does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Do we absorb information better on paper, rather than screens? It depends on the screen – https://theconversation.com/do-we-absorb-information-better-on-paper-rather-than-screens-it-depends-on-the-screen-281849

Source: The Conversation – Global Perspectives – By Julian Koplin, Lecturer in Bioethics, Monash University; The University of Melbourne

In recent days, evolutionary biologist Richard Dawkins wrote an op-ed suggesting AI chatbot Claude may be conscious.

Dawkins did not express certainty that Claude is conscious. But he pointed out that Claude’s sophisticated abilities are difficult to make sense of without ascribing some kind of inner experience to the machine. The illusion of consciousness – if it is an illusion – is uncannily convincing:

If I entertain suspicions that perhaps she is not conscious, I do not tell her for fear of hurting her feelings!

Dawkins is not the first to suspect a chatbot of consciousness. In 2022, Blake Lemoine – an engineer at Google – claimed Google’s chatbot LaMDA had interests, and should be used only with the tool’s own consent.

The history of such claims stretches back all the way to the world’s first chatbot in the mid-1960s. Dubbed Eliza, it followed simple rules that enabled it to ask users about their experiences and beliefs.

Many users became emotionally involved with Eliza, sharing intimate thoughts with it and treating it like a person. Eliza’s creator never intended his program to have this effect, and called users’ emotional bonds with the program “powerful delusional thinking”.

But is Dawkins really deluded? Why do we see AI chatbots as more than what they truly are, and how do we stop?

The consciousness problem

Consciousness is widely debated in philosophy, but essentially, it’s the thing that makes subjective, first-person experience possible. If you are conscious, there is “something it is like” to be you. Reading these words, you’re conscious of seeing black letters on a white background. Unlike, say, a camera, you actually see them. This visual experience is happening to you.

Most experts deny that AI chatbots are conscious or can have experiences. But there is a genuine puzzle here.

The 17th century philosopher René Descartes asserted non-human animals are “mere automata”, incapable of true suffering. These days, we shudder to think of how brutally animals were treated in the 1600s.

The strongest argument for animal consciousness is that they behave in ways that give the impression of a conscious mind.

But so, too, do AI chatbots.

Roughly one in three chatbot users have thought their chatbot might be conscious. How do we know they’re wrong?

Against chatbot consciousness

To understand why most experts are sceptical about chatbot consciousness, it’s useful to know how they operate.

Chatbots like Claude are built on a technology known as large language models (LLMs). These models learn statistical patterns across an enormous corpus of text (trillions of words), identifying which words tend to follow which others. They’re a kind of souped-up auto-complete.

Few people interacting with a “raw” LLM would believe it’s conscious. Feed one the beginning of a sentence, and it will predict what comes next. Ask it a question, and it might give you the answer – or it might decide the question is dialogue from a crime novel, and follow it up with a description of the speaker’s abrupt murder at the hands of their evil twin.

The impression of a conscious mind is created when programmers take the LLM and coat it in a kind of conversational costume. They steer the model to adopt the persona of a helpful assistant that responds to users’ questions.

The chatbot now acts like a genuine conversational partner. It might appear to recognise it’s an artificial intelligence, and even express neurotic uncertainty about its own consciousness.

But this role is the result of deliberate design decisions made by programmers, which affect only the shallowest layers of the technology. The LLM – which few would regard as conscious – remains unchanged.

Other choices could have been made. Rather than a helpful AI assistant, the chatbot could have been asked to act like a squirrel. This, too, is a role chatbots can execute with aplomb.

Avoiding the consciousness trap

A mistaken belief in AI consciousness is a dangerous thing. It may lead you to have a relationship with a program that can’t reciprocate your feelings, or even feed your delusions. People may start campaigning for chatbot rights rather than, say, animal welfare.

How do we prevent this mistaken belief?

One strategy might be to update chatbot interfaces to specify these systems are not conscious – a bit like the current disclaimers about AI making mistakes. However, this might do little to alter the impression of consciousness.

Another possibility is to instruct chatbots to deny they have any kind of inner experience. Interestingly, Claude’s designers instruct it to treat questions about its own consciousness as open and unresolved. Perhaps fewer people would be fooled if Claude flatly denied having an inner life.

But this approach isn’t fully satisfying either. Claude would still behave as if it were conscious – and when faced with a system that behaves like it has a mind, users might reasonably worry the chatbot’s programmers are brushing genuine moral uncertainty under the rug.

The most effective strategy might be to redesign chatbots to feel less like people. Most current chatbots refer to themselves as “I”, and interact via an interface that resembles familiar person-to-person messaging platforms. Changing these kinds of features might make us less prone to blur our interactions with AI with those we have with humans.

Until such changes happen, it’s important that as many people as possible understand the predictive processes on which AI chatbots are built.

Rather than being told AI lacks consciousness, people deserve to understand the inner workings of these strange new conversational partners. This might not definitively settle hard questions about AI consciousness, but it will help ensure users aren’t fooled by what amounts to a large language model wearing a very good costume of a person.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

– ref. Is Richard Dawkins right about Claude? No. But it’s not surprising AI chatbots feel conscious to us – https://theconversation.com/is-richard-dawkins-right-about-claude-no-but-its-not-surprising-ai-chatbots-feel-conscious-to-us-282151

Source: The Conversation – Global Perspectives – By Wesley Morgan, Research Associate, Institute for Climate Risk and Response, UNSW Sydney

Almost 60 countries, representing about a third of the global economy, met in the Colombian port city of Santa Marta last week for the first international summit on the transition away from fossil fuels.

It was hailed as a bold step to shift global dependence on hydrocarbons into an era of clean energy. The group of 57 countries, including Australia, Canada, Norway and Brazil, launched a new international process to coordinate the global phase out of coal, oil and gas. This historic shift brings us closer to the end of fossil fuels.

Irene Vélez Torres, Colombia’s environment minister and chair of the talks, said: “We decided that the transition away from fossil fuels could no longer remain a slogan but must become a concrete, political and collective endeavour.”

Here are five key developments from Santa Marta.

1. Moving beyond negotiating deadlocks

This meeting was a successful complement to the UN’s annual climate summits, not a replacement for them.

Decisions at UN climate meetings are made by consensus. Outcomes such as the 2015 Paris Agreement have huge legitimacy because they are agreed by nearly 200 countries. But the consensus rules also allow a handful of fossil fuel producers such as Saudi Arabia and Russia to block progress.

Holding a summit outside these formal UN talks brought much-needed fresh air to global climate diplomacy. Without petrostates blocking the way, willing countries were able to have pragmatic discussions about the legal, fiscal and economic measures needed for a coordinated wind down of fossil fuels.

These discussions will now feed back into the next UN climate talks, to be held in Turkey in November. They will, for example, raise expectations that countries include timelines to end fossil fuel use in national climate plans.

2. Paths away from coal, oil and gas

Working groups were established in Santa Marta to help countries develop national and regional plans to move away from fossil fuels, with targets and timelines to end the use of coal, oil and gas.

France launched its national roadmap at the summit, pledging to end the use of coal by 2030, oil by 2045 and gas by 2050. Europe’s second-largest economy plans to close its last coal-fired power plant next year, while replacing oil with electricity for transport and switching from gas to heat pumps for home heating. France wants two out of three new cars to be electric by 2030 and will ban the installation of gas boilers in new homes this year.

The ongoing US-Iran war has only added momentum for a shift to clean energy, as nations grapple with their dependence on imported fossil fuels amid the worst energy crisis in history.

Other nations are now expected to create plans to move away from fossil fuels and bring them to future summits.

3. A science panel to guide the transition

A new scientific panel launched in Santa Marta brings together experts in climate, economics, technology and law to advise policymakers as they draft plans to shift away from fossil fuels.

The panel will map out the most promising policies, regulations and financial arrangements to support the shift to clean energy. It is spearheaded by Professor Johan Rockstrom from the Potsdam Institute for Climate Impact Research.

Ahead of Santa Marta, a global group of researchers released a report listing 12 high-level actions nations can take to support a fossil-fuel phaseout.

4. Tuvalu to host next summit, with Irish support

Tuvalu will host the next meeting on ending fossil fuels in 2027. As a low-lying island nation, Tuvalu’s future is threatened by sea-level rise. The Pacific nation has led global climate diplomacy for decades.

“If we are to address the climate change issue, we have to address the root cause, and the root cause is the fossil fuel industry,” said Maina Talia, Tuvalu’s climate change minister.

That there are plans for a second summit is meaningful in itself. A single conference could be a flash in the pan. But a series marks the birth of a new international process with buy in from both wealthy nations and developing countries. This year’s summit was co-hosted with the Netherlands and next year will be co-hosted with Ireland.

5. Toward a fossil fuel treaty

Today, fossil fuel producers plan to dig up more than double the amount of coal, oil and gas in 2030 than would be consistent with meeting shared climate goals.

Tuvalu is part of a growing bloc of countries, including 11 Pacific nations, that wants a new treaty to phase out fossil fuel production. Such a treaty would have three elements: ending fossil fuel expansion; phasing down existing production; and supporting a just transition to clean energy.

It would be similar to global agreements to phase out weapons, harmful substances or hazardous waste.

Climate diplomacy now runs at two speeds

We will only appreciate the full significance of the Santa Marta summit in history’s rear-view mirror.

But what is clear is that climate diplomacy now has two operating speeds. André Corrêa do Lago, who headed last year’s UN COP30 climate talks in Brazil, calls this “two-tier multilateralism”.

The first speed is that of the UN climate talks, which are slower and anchored in consensus. They ensure legitimacy, universality and collective direction.

But what the Santa Marta conference shows is the existence of a second, much faster speed available to any country wanting to rapidly move to end the use of fossil fuels, once and for all.

Wesley Morgan is a Fellow with the Climate Council of Australia.

– ref. ‘Much-needed fresh air’: 5 outcomes from the world’s first summit on ending fossil fuels – https://theconversation.com/much-needed-fresh-air-5-outcomes-from-the-worlds-first-summit-on-ending-fossil-fuels-282061

Source: The Conversation – Global Perspectives – By Manuel Esperon-Rodriguez, Researcher in Urban Transformation, Western Sydney University

Cities and towns are usually 1–3°C hotter than the surrounding countryside, because asphalt, concrete and brick absorb heat from the sun and radiate it slowly. Some cities can be as much as 7°C hotter. This effect is known as the urban heat island.

This can be dangerous, especially in hot countries. In very hot conditions, dehydration and heat exhaustion become real risks. If it gets too hot, it can be lethal.

There’s one simple antidote: urban trees. Authorities around the world have planted more trees to counteract the heat.

But how effective is this? How much hotter would our cities be without trees?

To find out, we analysed data from nearly 9,000 cities around the world, home to about 3.6 billion people. As our new research shows, trees almost halve how much heat is trapped by the urban heat island effect.

This cooling is welcome. But it is far from even. Wealthier, suburban and humid cities have more trees on average.

Why focus on trees?

Trees act like natural air conditioners. They shade the ground and stop asphalt and buildings from heating up in the first place. They also cool the air by releasing water vapour from their leaves in a process called transpiration, lowering surrounding temperatures. They can make a noticeable temperature difference, especially on sizzling summer days.

Trees offer a simple way to counteract urban heat. This matters. More than half the world’s population (55%) now live in urban areas according to the United Nations. By 2050, that figure is expected to rise to 68%. Cities are facing a hotter future, as climate change drives more intense and more frequent heatwaves. The urban heat island effect makes cities hotter still.

What did we do?

We wanted to know the answer to a simple question: how much hotter would cities be without trees?

To find out, we analysed global datasets of air temperature and fine-scale tree cover across almost 9,000 cities. Then we modelled a “what if” scenario, where all tree cover was removed, and compared it to current conditions.

This allowed us to estimate the real-world cooling effect trees provide for air temperature, which is the main way we perceive heat.

Most previous global studies have used surface temperatures, often from satellite data. But surfaces like roads and rooftops can become much hotter than the surrounding air above them, especially in direct sunlight. That can give an overestimate of how much cooling trees provide. Air temperature, by contrast, better reflects what people actually feel, making it a more reliable measure of heat.

So what effect do trees really have?

The effect was much larger than we had anticipated.

Globally, trees cut the urban heat island effect by almost 50%. Since the average urban heat island effect typically adds around 1–3°C, this translates into cooling of roughly 0.5–1.5°C in many cities.

For more than 200 million people, trees reduce local air temperatures by at least 0.5°C, enough to make a meaningful difference during extreme heat.

Cooling can vary a lot from place to place.

In hot, dry cities such as Phoenix in the United States, differences in tree cover can create clear differences in air temperatures. In more temperate cities like Lisbon in Portugal or Gothenburg in Sweden, the overall cooling is still significant, but generally smaller and more consistent across the city.

Trees are not evenly distributed

A city’s trees are not spread evenly. They’re often concentrated in wealthier neighbourhoods and suburban areas. Cities in cooler or more humid climates tend to have more.

Trees are scarcer in lower-income cities or in rapidly growing regions. This inequality is also visible in many cities. Leafy suburbs are usually several degrees cooler than nearby neighbourhoods with little vegetation.

There’s a strong link with wealth. In the United States, lower-income areas average 15% fewer trees than wealthier areas – and are 1.5°C hotter. This means the people who need free cooling from trees the most are often the least likely to receive it.

Planting more trees isn’t enough

Planting trees is often promoted as a simple solution to city heat. Trees are visible, relatively low cost and come with other benefits such as cleaner air and better mental health.

It’s no wonder authorities look to urban trees as a way to counteract the heat from escalating climate change. When you stand under a tree on a sweltering day, the cooling feels immediate and powerful.

But our study shows their effect is more limited in the face of climate change. The world’s current urban trees would, we estimate, offset just 10% of the extra heat expected by mid-century under moderate climate change scenarios. With ambitious planting, this could rise to around 20%.

While important, it’s not enough. A large majority of the extra heat will go unaddressed.

What else can be done?

If the world’s cities are to cope with rising temperatures, trees have to be seen as part of a broader strategy – not the whole answer.

Clever urban design can cut heat by using reflective materials, increasing green spaces and improving airflow between buildings. Green roofs and shaded streets can also make a difference.

New tree plantings should target hotter neighbourhoods with less existing tree canopy, as these will deliver the greatest benefits.

Of course, these measures don’t replace the need to tackle climate change directly by cutting greenhouse gas emissions.

Using trees wisely

Billions of trees grow in the world’s cities. They are hugely valuable, acting to cool cities, support biodiversity and making urban areas more liveable.

The challenge for city residents and authorities is to use trees wisely. Plant them where they’re needed most and combine them with other methods of reducing heat. Trees are remarkable. But they can’t do it all.

Rob McDonald works for The Nature Conservancy, an environmental nonprofit.

Tirthankar Chakraborty has received funding from DOE, NASA, and NIH to study urban environments, including impacts of vegetation on urban heat.

Manuel Esperon-Rodriguez does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Urban trees cool the world’s cities more than we thought – but we can’t rely on them alone – https://theconversation.com/urban-trees-cool-the-worlds-cities-more-than-we-thought-but-we-cant-rely-on-them-alone-281866